I'd rather do fiberglass, though I've never done it before, I'm pretty sure I'd be able to.
1st problem is my limited space. Yeah, I have a pretty large trunk, but I'm not gonna cover up the spare tire well. I can go about 1/4 the way over it, but no further. I have to be able to get to that tire when I need to.
Taking out the back seats is also not an option. I bought a sedan because I use the rear seats and back doors.
What I think is the best option (with limited knowledge) would be to take out the mat (taken out for the picture) and cutting the plastic-carpeted floorboad in half. I could put it on a hinge, then put the mat back over it. That way, I can 'glass the back half, and still be able to open up my trunk when I need to.
The second problem I have with fiberglass is what happens when you want to upgrade your subs, amps, etc.? Do you tear it down and start over?
Lastly, how the hell are you supposed to measure a fiberglass enclosure?
Pictures of trunk and wheel well:
I know you know what a trunk looks like, but maybe some specifics are needed for someone that can help.